Owing to a physical size and/or material makeup of an antenna or frequency selective surface (FSS) element, a specific range of excitation frequencies (or its operational bandwidth) is required to efficiently drive the antenna. Hence, a first antenna or FSS element having a first dimension and material makeup can be driven by a first set of excitation frequencies and a second antenna or FSS element having a second dimension and material makeup, different from the first, can be efficiently driven by a second set of excitation frequencies. However, it is not efficient for the first set of frequencies to drive the second antenna or FSS element, and similarly it is not efficient for the second set of frequencies to drive the first antenna or FSS element. Inefficient excitation by an electromagnetic source from an attached generator or by free-space radiation results in poor radiated or received power, respectively.
Further, efficient excitation for long wave (low-frequency) transmission requires larger antenna or FSS elements than efficient excitation for short wave (high-frequency) transmission. Hence, the ability of an antenna or FSS array to operate at longer wavelengths can be limited by the size of its antenna or FSS element(s) if they were designed for efficient transmission of short wavelength signals.